Pavement on streets, highways, airstrips and the like is subject to wear and deterioration from, among other forces, the repeated travel of vehicles thereon. In the case of highways, one kind of deterioration, which is prevalent on well-traveled strips of pavement, is faulting at the transverse expansion joints between adjacent slabs of pavement. Where the wheel paths intersect the transverse joints, the pavement is known to suffer repeated heavy loading due to the passage of traffic. As a result, the pavement around the transverse joints is subject to a type of premature fatigue failure known as faulting.
Load transfer restoration (LTR) is known to improve load transfer across a joint and reduce the rate of future fault development. Joint load transfer is the capacity of a joint to distribute an approaching load by shear from one pavement slab to the adjacent pavement slab. The ability of a joint to distribute load is fundamental to its performance, with poor load transfer typically evidenced by a loss of structural integrity, such as faulting and, if not corrected, cracking and crumbling of the pavement near the joint.
One type of load transfer restoration (LTR) currently used in the industry is to utilize mechanical load transfer devices, such as steel dowel bars, in a process known as dowel bar retrofitting. Generally described, dowel bar retrofitting begins with creating aligned slots, typically one at a time, which straddle the transverse joint lines between adjacent pavement slabs. The slots are typically cut by a saw in the vehicle wheel paths, parallel to the pavement centerline and with each other. This is usually accomplished using saws equipped with diamond-impregnated blades that cut a single slot of the desired width and length, until all of the slots are formed. Once the slots are cut, the “plug” or remaining portion between the cuts is removed, usually by a jackhammer. Next, the slots are prepared to receive backfill material used to fill in the slots after the dowel bars have been installed. To prepare the slots, the slots are sand blasted to create slot surfaces that will establish a good bond between the backfill and slot walls, since a good bond is essential for load transfer performance. Once the preparation of the slot is complete, the dowel bars are inserted into the slots, and covered by backfill material.
One method of improving the speed and cost of dowel bar retrofitting is described in U.S. Pat. No. 5,492,431, to Rasmussen et al. Rasmussen et al. purportedly disclose a machine using twelve (12) wet cutting saw blades for simultaneously cutting sets of slots in the pavement. The blades move fore and aft on a carriage, and vertically up and down to cut the outer edges of the slots. Once the machine is finished cutting the slots, the machine moves to the next joint line to repeat the process, while a crew of men continue the process of removing the “plug,” as well as preparing the slots prior to insertion of the dowel bar and backfill material.
While the machine of Rasmussen et al. provides the improved results of simultaneously cutting the slots using a single machine, the process of dowel bar retrofitting utilizing such a machine still has its disadvantages. For example, the blades of such a machine can become dull or break during constant usage, thereby requiring frequent and expensive replacement. Additionally, after such a machine is finished, the process still requires manual removal of the “plug” and preparation (e.g., sandblasting) of each slot so that the slots may be used for dowel bar retrofitting. The removal of the “plug” and preparation of the slots typically requires additional crew members at additional man-hours, which increases the cost and time required for completing the job.